Einstein’s time dilation apparent when obeying the speed limit

General and special relativity are two of the more mind bending theories in modern science. According to them, space and time are a singular entity that is warped by mass, where measurements completely depend on how the person doing the measuring is moving. People generally believe that relativity has no effect in everyday life, since it's generally discussed in terms of things going very fast or objects in highly warped spacetime.

This belief is not entirely true—GPS equipment would not work if the times measured by the satellites were not corrected for time dilation that arises from the rapid motion of the satellites relative to your car. In general, though, most people go about their day without experiencing any ill- (or odd-) effects due to relativity. However, it turns out that, if you can measure accurately enough, the effects of relativity are indeed all around us.

Using the most accurate clocks in existence, a team of researchers at NIST in Boulder, CO have shown that relativity all around us—even on everyday lab scales. The team used an optical "quantum logic clock" that is based on an electron's oscillations between the 1s and 3p quantum energy levels of an 27Al+ ion. A pair of these clocks—each of which will lose less than one second every 3.7 billion years—were tethered together by a special optical cable connecting two adjacent labs. The clocks were then manipulated so that time dilation occurred.

The first experiment had one clock moving relative to the other, a situation that is used to introduce the concept of time dilation to introductory physics students—faster moving clocks will tick away more slowly. In this case, one clock's ion was put in motion relative to the other, and the frequency shift that resulted was measured. Even when the clocks were moving apart at 22.4 miles per hour, it was possible to observe a change in frequency of approximately 45x10-17. This is exactly in agreement with the predictions of special relativity.

A lesser known consequence of general relativity is that time will move slower in a stronger gravitational field. On Earth, one implication of this is that a clock on the second floor of an office building will move faster than one on the first floor. Using the ultra-precise clock setup, the NIST researchers tested this as well. One of the optical clocks was placed about a foot above the other and measurements were taken. They found a fractional frequency change of (4.1±1.6)x10-17; plugging this number back into relativity's formulas produced an equivalent height differential gave 14.5±5.9 inches, a result that nicely bracketed the 12 inch difference in the experimental setup.

I am no physicist and I do not understand how time is related to anything physical, or how it "slows." To me, time is a concept man has created because it is useful. It doesn't seem inherent to the universe at all. If you want to say the man travelling at the speed of light for 50 years ages slower than the man on earth, or that an atomic clock ticks slower (by measuring oscillations), doesn't this just mean that EVENTS are occurring at a slower pace? How does this affect the concept of "time"? On a larger scale it's like saying my clock's pendulum swings at one speed, and then swings at a slower speed, and claiming that that is proof of time slowing down. It isn't - the event is just happening more slowly.

I know that time is in fact related to space, as Einstein is absolutely smarter than me, I'd just like to be able to understand how.

On a larger scale it's like saying my clock's pendulum swings at one speed, and then swings at a slower speed, and claiming that that is proof of time slowing down. It isn't - the event is just happening more slowly.

It's not slowing down ... for you. You always see the pendulum at the same speed. They guy who just stole your car sees it change speed though.

I originally wanted to post a side note about being disappointed in NIST's faulty explanation of WTC7 collapse, but I received a 503 error and was wondering if the Ars filters thought it was too crazy or off-topic.

Time dilation is certainly nonsense since time cannot change by definition. Clocks do slow down for whatever reason having to do with energy conservation but time itself is always invariant. Time dilation is therefore a misnomer. The amazing truth, the one that always takes Einstein's defenders by surprise, is that a time dimension makes motion impossible. This is the reason that nothing can move in spacetime and that Karl Popper called spacetime, “Einstein’s block universe in which nothing happens.” Source: “Conjectures and Refutations”. I ain’t making this stuff up. Google it and be enlightened.

And while you’re at it, try Googling “How to Falsify Einstein’s Physics, For Dummies” to find out how Einstein’s ideas on space and time have retarded progress in physics for close to a century.

I hope I could understand any of the relativities (be it general or special)

By the way, does anyone know at which speed do electrons orbit the nucleus? Are they also affected by relativity?

In normal matter the electrons are not travelling at a significant percentage of c - but as this experiment shows they will still be affected. Just not by very much. In white dwarf matter the electrons are zipping about at a decent percentage of c.

On a larger scale it's like saying my clock's pendulum swings at one speed, and then swings at a slower speed, and claiming that that is proof of time slowing down.

A pendulum may slow down but it goes back and forth at a pretty steady rate. By slowing down it covers less distance, which makes up for the speed it loses in shortening the distance it has to travel. The regularity of a pendulum is why they were so useful in mechanical clocks as a measure of time. I know, kind of nit-picky, but the entire point of a pendulum is that it doesn't matter how fast it's going: it's still counting off a regular cycle.

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It isn't - the event is just happening more slowly.

So time is slowing down if the events are happening more slowly.

Think of it this way: instead of a pendulum, imagine a clock that bounces light back and forth between two mirrors. As long as the clock is perfectly still relative to you, it will always measure the same time because it's not having to cover any extra distance. But if you move the clock perpendicularly to the motion of the light's bouncing, the light doesn't just have to cover a regular back-forth but also an up-down distance as well (the diagonal between two corners of a square is longer than the distance from one edge to the other, see?). Since light always travels the same speed, now that it's covering more distance it takes longer for the clock to tick-tock from where you're standing. Light's speed is a universal constant, the same no matter where you are or how fast you're going in relation to it. Since the speed of the light doesn't change in the light-beam clock, but the tick-tock is still slowing down, it must be time that is changing. To you, the clock is slowing down. To the clock, you are the one that appears to be going slower (not sped up, as you would probably have assumed). That's because motion through space is relative: it makes no difference if you're the clock moving relative to the observer, or the observer moving relative to the clock: time dilation applies from either "frame of reference."

Time isn't a constant that's the same throughout the Universe. The speed of light demonstrably is constant regardless to your frame of reference (standing still, moving away from the light, moving with the light, etc.). If things did not work this way, the atomic clock experiment here wouldn't have worked out the way it did.

So, a guy was speeding on his way to work trying to make a meeting on time, and does through an intersection only to get caught by a cop. The cop said he stopped him for breaking a red light, but the guy swore the light was green when he went through the intersection.

If both of then are telling the truth, how fast was the guy driving?

(I know, time dilation and doppler effect aren't the same thing.. just wanted to share anyway )

I don't understand either. Great, increasing the distance increases the time to travel it, I got that much. I can grasp that gravity would have an effect on a classic clock with hands. What I don't understand is how any of this affects ACTUAL time. Not measurements of time distorted by physical limitations on tools. 1 second is 1 second. When you guys say time slows down, you make me think you're saying 1 second takes 2 seconds.

A minor nit pick, but for GPS general relativity has a greater effect than special. General relativity makes the clocks on the satellites "speed up" more than special makes them slow down. Only for satellites orbiting less than a couple hundred KM is special stronger.

So, a guy was speeding on his way to work trying to make a meeting on time, and does through an intersection only to get caught by a cop. The cop said he stopped him for breaking a red light, but the guy swore the light was green when he went through the intersection.

If both of then are telling the truth, how fast was the guy driving?

(I know, time dilation and doppler effect aren't the same thing.. just wanted to share anyway )

When that happened to me, I claimed it was a trick question since the fine for doing near the speed of light in a playground zone is more than that of running a red light.

I hope I could understand any of the relativities (be it general or special)

By the way, does anyone know at which speed do electrons orbit the nucleus? Are they also affected by relativity?

One must use notions of speed and velocity when talking about electrons with care, but in a (very) rough sense you can say that when electrons are bound to a highly charged nucleus (heavier elements like gold), the electrons are "orbiting fast enough" that you need to treat them relativistically. The resulting contraction of the s orbitals in gold lowers the energy of d->s excitations into the visible range, giving it its color. Electrons also see part of the nuclear electric field as a magnetic field, which allows for spin-orbit coupling which is also more pronounced for heavy elements.

I am no physicist and I do not understand how time is related to anything physical, or how it "slows." To me, time is a concept man has created because it is useful. It doesn't seem inherent to the universe at all. If you want to say the man travelling at the speed of light for 50 years ages slower than the man on earth, or that an atomic clock ticks slower (by measuring oscillations), doesn't this just mean that EVENTS are occurring at a slower pace? How does this affect the concept of "time"? On a larger scale it's like saying my clock's pendulum swings at one speed, and then swings at a slower speed, and claiming that that is proof of time slowing down. It isn't - the event is just happening more slowly.

I know that time is in fact related to space, as Einstein is absolutely smarter than me, I'd just like to be able to understand how.

correct that time is a man made concept.

your example would be correct with the pendulum if we say it has a constant swing. but this slow down is happening to everything in that frame of reference the pendulum is in.

but to someone outside that frame, time would take a different meaning, and perceive you as moving faster or slower depending on the case.

Time dilation is certainly nonsense since time cannot change by definition. Clocks do slow down for whatever reason having to do with energy conservation but time itself is always invariant.

The speed of light is invariant, not time. If "time dilation" were not real, this experiment wouldn't have worked and GPS signals wouldn't need corrections and pretty much everything you try to use to dismiss it would be non-functional anyway. "Conservation of energy" doesn't explain it the universal speed of light.

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Time dilation is therefore a misnomer. The amazing truth, the one that always takes Einstein's defenders by surprise, is that a time dimension makes motion impossible. This is the reason that nothing can move in spacetime and that Karl Popper called spacetime, “Einstein’s block universe in which nothing happens.” Source: “Conjectures and Refutations”. I ain’t making this stuff up. Google it and be enlightened.

I tried googling this phrase and the only things that turn up are you posting comments everywhere and other people posting almost identical comments. Frankly, knowing that Popper help up general relativity as an example of a successfully tested theory, I don't see how you're getting this out of him unless Popper were wrong (it's been known to happen; for a long time he thought Darwinian evolution was unfalsifiable but later changed his mind once he got the right idea about it) or you're wrong about Popper's statement.

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And while you’re at it, try Googling “How to Falsify Einstein’s Physics, For Dummies” to find out how Einstein’s ideas on space and time have retarded progress in physics for close to a century.

I don't understand either. Great, increasing the distance increases the time to travel it, I got that much. I can grasp that gravity would have an effect on a classic clock with hands. What I don't understand is how any of this affects ACTUAL time. Not measurements of time distorted by physical limitations on tools. 1 second is 1 second. When you guys say time slows down, you make me think you're saying 1 second takes 2 seconds.

It is relative to the moving person. If two people are moving relative to each other (the faster the better), each person measures time as they always have. It always appears as one second by all measurement for each of them in their own frame of reference.

But, when they compare clocks, the time values do not match.

It has nothing to do with physical limitation on the tools, and in fact the more accurate the tools, the more apparent the effect.

Depends on your frame of reference. That's the whole point of Relativity. Sounds like you're complaining when you haven't even read the very basics of the theory.

I'm not complaining about anything? And no I haven't studied physics.

And yes, you guys throw the frame of reference around, but there's never been a time where I went 80 mph to work, and my friend went 60mph and one of us said, WOW, you broke the time barrier. No, my friend, I just drove faster. And you're late to work. I clearly don't understand this theory. And at my age I probably won't ever.

I'm not saying the theory is wrong, and I trust that it's correct. I'm just saying I don't get it.

This story is really about how great the new atomic clocks (or whatever they call them now) are, and not about relativity.

That's not at all true. It's about how great new atomic clocks are, and that you can now measure the effects of Relativity even at highway speeds rather than "nearer to the speed of light". It's about making relativity accessible to everyone, just as soon as we can buy those atomic wrist watches at walmart.

This story is really about how great the new atomic clocks (or whatever they call them now) are, and not about relativity.

Agreed. The fact that they can move the clocks by a foot and measure the difference it makes is awesome, and everybody who cares about physics knows that relativity holds up anyway.

That makes them blind faith fanatics.

I want proof. It's part of that science thing. I don't give a fuck that someone else can prove it near the speed of light. I like that we are moving toward a world in which I can make it real and observable for me in my 72 Chevy Vega. Once it gets over 22 mph that is.

Sykus: You have to think of the 3 'regular' dimensions along with 'time' being the 4th. The total 'velocity' you can have is equal to c. So, X + Y + Z + time = c.

If you start moving faster on the X/Y/Z axes, you have to subtract velocity from the time axis to keep the equation balanced. Otherwise you move 'faster-than-light' which isn't allowed.

However, observations of your movement through the space-time continuum are only 'valid' for those in the same frame of reference. Someone who isn't moving will record your various velocities differently than someone else who is moving, who again will be different than you. Wrapping your head around frames of reference is only slightly less difficult than understanding quantum mechanics

Depends on your frame of reference. That's the whole point of Relativity. Sounds like you're complaining when you haven't even read the very basics of the theory.

I'm not complaining about anything? And no I haven't studied physics.

And yes, you guys throw the frame of reference around, but there's never been a time where I went 80 mph to work, and my friend went 60mph and one of us said, WOW, you broke the time barrier. No, my friend, I just drove faster. And you're late to work. I clearly don't understand this theory. And at my age I probably won't ever.

I'm not saying the theory is wrong, and I trust that it's correct. I'm just saying I don't get it.

Einstein put a small book out, written for non science types (me) but who do have an interest in science.

Relativity: The Special and the General Theory

he keeps the formulas to a minimum, but ignoring those, the concepts discussed are a great read.

Depends on your frame of reference. That's the whole point of Relativity. Sounds like you're complaining when you haven't even read the very basics of the theory.

I'm not complaining about anything? And no I haven't studied physics.

Relativity and time dilation are a lot easier to wrap your head around if you remember this: Everybody in the Universe, no matter how fast they're moving, or where they are, agrees that light travels at the same speed.

If you watch a train go by which is travelling at half the speed of light, and the conductor turns on the headlight, both you and the person inside will both agree that the light from the headlight is travelling at the same speed (C). This is counter-intuitive to the common belief of adding the train's velocity to that of the light's.

The only way the math works out, is if time travels slower for objects as they approach the speed of light. And this test is the latest in the gazillions of tests they've performed that verify this.

The way I think of it is this: Everything is at all times travelling at the speed of light through spacetime. The more speed you "divert" towards moving through space, the more speed you're diverting from travelling through time.

I have no idea how close that model is to reality, but it make a little sense to me at least.

Time dilation is certainly nonsense since time cannot change by definition. Clocks do slow down for whatever reason having to do with energy conservation but time itself is always invariant.

The speed of light is invariant, not time. If "time dilation" were not real, this experiment wouldn't have worked and GPS signals wouldn't need corrections and pretty much everything you try to use to dismiss it would be non-functional anyway. "Conservation of energy" doesn't explain it the universal speed of light.

Well I also googled and at the end ended up with the following "proof": " Why is motion in spacetime impossible? It has to do with the definitions of space and time and the equation of velocity v = dx/dt. What the equation is saying is that, if an object moves over any distance d x, there is an elapsed time d t. Since time is defined in physics as a parameter for denoting change (evolution), the equation for velocity along the time axis must be given as v = dt/dt which is self-referential. The self-reference comes from having to divide dt by itself. dt/dt always equals 1 because the units cancel out. This is of course meaningless as far as velocity is concerned." (src(

I may not have studied physics, but I'm not too bad with math, not that it would help anything here because of that large non sequitur right in there..

Matt Ford / Matt is a contributing writer at Ars Technica, focusing on physics, astronomy, chemistry, mathematics, and engineering. When he's not writing, he works on realtime models of large-scale engineering systems.